To understand the mechanism of current-confined-path formation for the current-perpendicular-to-plane type of giant magnetoresistive devices, we have investigated the evolution of an A1 monolayer on the Cu (111) surface both by in situ scanning tunneling microscopy and by molecular dynamics simulation. Ultrathin A1 nano-clusters were formed on the plateaus and step (or plateau) edges of the Cu surface in the as-deposited state. Upon annealing at 300 ° C, A1 atoms migrated toward the step edges by surface diffusion. As a consequence, nanometer-sized Cu channels not covered by A1 clusters can be formed. These channels could serve as current-confined paths if subsequent mild A1 oxidation is provided.
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